Staple fibre fabrics and method of making the same

ABSTRACT

The invention provides for a yarn or fabric containing bicomponent staple fibers wherein the staple fibers comprise two components existing in a sheath/core relationship, the core component having a lower melting point than the sheath component. Upon heat treatment the core component softens and exudes from the cut end portions of the staple fibers and bonds to adjacent fibers on cooling.

United States Patent Inventor Raymond George Gosden Pontypool, England Appl. No. 17,222 Filed Mar. 6, 1970 Patented Oct. 26, 1971 Assignee Imperial Chemical Industries Limited London, England Priority Mar. 12, 1969 Great Britain 13,022/69 STAPLE FIBRE FABRICS AND METHOD OF MAKING THE SAME 9 Claims, 1 Drawing Fig.

[56] References Cited UNITED STATES PATENTS 2,987,797 6/1961 Breen 161/175 3,317,368 5/1967 Battersby l6l/175 3,420,731 1/1969 Kuhn 57/140 BY Primary ExaminerRobert F. Burnett Assistant ExaminerLinda C. Koeckert Attorney-Cushman, Darby & Cushman STAPLE FIBRE FABRICS AND METHOD OF MAKING THE SAME The present invention relates to the manufacture of textile fabrics, especially knitted and woven fabrics, containing staple fibers.

Fabrics formed from staple fibers, especially short-length staple fibers, have a marked tendency for some of the fibers to pull out from the surface of the fabric during use. This is generally referred to as "cob-webbing in nonwoven fabrics. ln fabrics knitted or woven from staple-fiber yarns,'the fibers pulled out from-the surface often tend to form small balls on the surface of the fabric, this effect is referred to as pilling."

We have now found that this tendency for fibers to become detached from the surface of the fabric may be'alleviated by using staple fibers formed from filaments containing two components existing in a sheath/core relationship, the core 'component having a lower melting point thanthe sheath component andthe yarns or fabrics prepared therefrom to cause the core componenthaving a lower melting point than 'the sheath component and the yarns or fabrics. prepared therefrom to cause the core component to soften and exude from the cut end, portionsof the staple fibers and bond to adjacent fibers in cooling.

Accordingly, therefore, the present invention provides a yarn or textile fabriccontaining bicomponent staple fibers whereinthe staple fibers comprise two components existing in a sheath/corerelationship, the core component having a lower melting point than the sheath component, and the end portions 'ofthe fibers are bonded to other fibers in the yarn or fabric.

Preferably the yarn or fabric contains at least 50 percent by weight-of the bicomponent staple fibers and the said fibers contain at. least 25 percent by weight of the component forming the core.

Froni another aspect the invention provides a process for the manufacture of a yarn or textile fabric as defined above, forming a yarn or fabric'from the said bicomponent staple fibers, subjecting it to a heat treatment at a temperature above the melting point of the core component and below themelting point of the sheath component of the staple fibers to cause the said core component to softenand exude from the end portions thereof and contact adjacentfibers, and cooling the yarn or fabric to a temperature belowthe melting point of the core component.

The present invention is'of particular value when applied to knitted, woven or nonwoven fabrics formed from staple fibers which fabrics are normally liable to pilling.

The term "pilling" as applied to fabrics is well known, being the formation of smallballs of tangled fibers forming on the surface of fabrics during use. Filling is associated with fabrics containing staple fibers,-and our invention is especially applicable to fabrics containing a sufficiently high proportionof staple fibers of short lengths such that pilling is normally a problem.

The fabrics may, of course, be fabricated entirely from bicomponent sheath/core staple fibers. lf knitted or woven fabrics are to contain only a proportion of such bicomponent fibers, that proportion may be introduced in the form of yarn of mixed staple fibers oras a yarn of wholly bicomponent sheath/core staple fibers used together with a yarn of other composition, for example in a warp and weft relationship.

By having a lower melting point" we mean that the core polymer is of a melting point sufficiently below that of the sheath so that itmaybeensured that the fabric may conveniently be exposed to thermal conditions which result in the core component being raised to a temperatureabove its melting point whilst at the same time temperature of the sheath component remains below its melting point and is substantially unaffected by the heating.

The duration of the thermal treatment need be no longer than that required to melt the core component and can be easily ascertained by simple tests.

Bonding is achieved at the end portions of the fibers and not at crossover points of fibers as with prior art bonding techniques, since when the fibers are heated to a temperature above the melting point of the core, the latter oozes out from the ends of the fiber which then bond onto adjacent fibers on cooling. v I V The-fibers in a yarn maybe bonded by passing the yarn over a heated plate and fibers in a fabric may be bonded by treating the fabric in an air-oven.

A ny suitable combination of polymers may be employed as the sheath or core componentsprovided that there is good adhesion therebetween. Poor adhesion results in weak bonds being formed which may be readily broken and thereby reduce the effectiveness of the present invention.

Suitable combinations of polymers include, for example, polyethylene terephthalate, of melting point 260 and a copolyester of ethylene terephthalate and ethylene'iso'phthalate containing 60 ethylene terephthalate units to 140 ethylene isophthalate unitsin the molecule and having a melting point of 140 C. Other suitable combinations include polyhexamethylene adipamide and a copolymer of polyhexamethylene adipamide and polyhexamethylene isophthalamide in a 7050 weight ratioand also poly hexamethylene adipamide and a copolymer of polyhexarnethylene adipamide and polyepsilon caprolactam in a weight ratio of 60:40.

The core may be located concentrically or eccentrically in the sheath.

the following examples illustrate but do not limit the invention.

EXAMPLE 1 mide in a weight ratio of 70:30 by melt-spinning in conventional equipment. The tow is convened into a 3 d.p.f. Ila-inch staple fiber and spun into a 400-denier yarn on a Shirley Miniature Spinning Machine. The spun yarn is passed continuously over a hot plate at 200 C. with a dwell time of seconds. Bonding of the fibers occurs between the cut end of one fiber andan adjacent fiber in the manner shown in FIG. A.

EXAMPLE 2 Three d.p.f. 4-6-inch crimped staple fibers, formed from bicomponent filaments in which the components exist in a sheath/core relationship, the sheath being polyhexamethylene adipamide and the core a copolymer' of polyhexamethylene adipamide and polyepsilon caprolactam in a 70:30 weight ratio (melting points 262 and 205C. respectivelyyandwhich bicomponent filaments have different core/sheath ratios, and 3 d.p.f. 4-6-inch polyhexamethylene adipamide staple fibers were spun to 2'fold/l8s worsted count, 6 t.p.i. singles twist and 3 t.p.i. doubles twist. Five yarns were spun from the following blends:

l. percent bicomponent staple fibers having a 50:50 core/sheath ratio by weight.

2. 100 percent bicomponent fibers having a 30:70 core/sheath ratio by weight.

3. A blend of 50 percent bicomponent staple fiber (50:50

' core/sheath) and 50 percent 6.6 nylon fibers.

4. A blend of 30 percent bicomponent (50:50 core/sheath) and 70 percent nylon 6.6 staple fiber.

5. A blend of IS percent bicomponent fiber (50:50 core/sheath) snd85 percent 6.6 nylon staple fiber.

Samplesof yarn from each blend were knitted twofold on a iii-gauge hand flat bed knitting machine. Two' samples of each yarn were knitted, one being bonded in a hot air oven at 230 C. for 60 seconds, the other being used as a control sample. Fourbonc'led and unbonded fabric panels were examined for hairiness" afier mild abrading treatment. the degree of hairiness" being taken as an indication of the tendency of the fabric to Pill."

Bonded fabric prepared from blends containing at least 50 percent bicomponent staple fibers were less hairy than the unbonded control samples, but below 50 percent there was no significant difference between the bonded and control samples.

Bonded fabrics formed from the bicomponent staple fibers having a core/sheath ratio of 30:70 were slightly less hairy than the unbonded control samples.

EXAMPLE 3 withdraw the fiber from the yarn recorded and compared with the force required to remove the fiber from a sample of unbonded yarn. The mean of 9 tests was taken.

The test was carried out on three yarns having core/sheath ratios of 50:50, 25:75 and :85, the results of these tests are given in table 1.

TABLE I Yarn Force to Withdraw (g.)

Bonded Yarn Unbonded Yarn 50/50 core/sheath 7.8 0.23 25/75 core/sheath 3.9 0.28 15/85 core/sheath 0.39 0.31

These results clearly demonstrate the advantage accruing from bonding the bicomponent fibers in the yarn where the core/sheath ratio is 25:75 or higher with respect to core proportion.

EXAMPLE 4 Four d.p.f. 4-6-inch crimped sheath/core bicomponent staple fibers having, as the sheath component, polyethylene terephthalate (softening point 265 C.) and as the core component a polyethylene terephthalate/isophthalate (60:40, mole ratio) copolymer (softening point 140 C.) having a 50:50 and 75.25 (by weight) sheath/core ratios were spun on the worsted system to twofold 36s worsted count yarns. The yarns were woven across the warp of polyethylene terephthalate filament yarn in a 2:2, twill weave.

The fabrics were subjected to the "Atlas" pill test and examined after one hour, the degree of pilling being assessed subjectively against known standards (Standard 1 has excellent pilling resistanceStandard 3, poor). The test results are 25/75 core/sheath 2 3 fered from that in the publication only in that the chamber was lined with cork one-eighth inch thick and the impeller rotated at l,080 revs/min.

EXAMPLE 5 Six d.p.f. bicomponent staple fibers of example 2 having a 50:50 core/sheath ratio were carded into a web and the web passed through a hot air oven at 230 C. at such a speed that the residence time in the oven was 60 seconds. immediately after leaving the oven the web was passed through the nip of a pair of cold calendar rolls. The resultant bonded nonwoven fabric had good drape and strength.

What i claim is:

l. A textile article being a yarn or fabric containing bicomponent staple fibers wherein the said staple fibers comprise two components existing in a sheath/core relationship, the core component having a lower melting point than the sheath component and said article having been heat-treated to cause the core component of the staple fibers to exude from the ends thereof and bond the end portions of the fibers to other fibers in the yarn or fabric.

2. A textile article according to claim 1 comprising at least 50 percent by weight of bicomponent staple fibers.

3. A textile article according to claim I wherein the bicomponent staple fibers contain at least 25 percent of the core component.

4. A textile article according to claim 1 wherein the bicomponent fibers are polyamide fibers and comprise, as a sheath component, polyhexamethylene adipamide and as the core component polyepsilon caprolactam in a :30 weight ratio.

5. A textile article according to claim I wherein the fibers and comprise, as the sheath component, polyhexamethylene adipamide and, as the core component, a copolymer of polyhexamethylene adipamide and polyhexamethylene isophthalamide in 70:30 weight ratio.

6. A textile article according to claim 1 wherein the fibers are polyester fibers and comprise, as the sheath component, polyethylene terephthalate and as the core component, a copolymer of polyethylene terephthalate and polyethylene isophthalate in 40:60 mole ratio.

7. A process for the manufacture of a textile article from bicomponent staple fibers comprising forming the yarn or fabric from bicomponent staple fibers in which the components exist in a sheath/core relationship and the core component has a lower melting point than the sheath component, subjecting it to a heat treatment at a temperature above the melting point of the said core component and below the melting point of the said sheath component of the bicomponent staple fibers to cause the core component to soften and exude from the end portions thereof and contact adjacent fibers, and cooling the yarn or fabric to a temperature below the melting point of the core component.

8. A process according to claim 7 wherein the yarn to be subjected to the heat-treatment is passed over a heated plate.

9. A process according to claim 7 wherein the fabric to be subjected to a heat treatment is treated in an air oven.

III i t i 

2. A textile article according to claim 1 comprising at least 50 percent by weight of bicomponent staple fibers.
 3. A textile article according to claim 1 wherein the bicomponent staple fibers contain at least 25 percent of the core component.
 4. A textile article according to claim 1 wherein the bicomponent fibers are polyamide fibers and comprise, as a sheath component, polyhexamethylene adipamide and as the core component polyepsilon caprolactam in a 70:30 weight ratio.
 5. A textile article according to claim 1 wherein the fibers are polyamide fibers and comprise, as the sheath component, polyhexamethylene adipamide and, as the core component, a copolymer of polyhexamethylene adipamide and polyhexamethylene isophthalamide in a 70:30 weight ratio.
 6. A textile article according to claim 1 wherein the fibers are polyester fibers and comprise, as the sheath component, polyethylene terephthalate and as the core component, a copolymer of polyethylene terephthalate and polyethylene isophthalate in a 40:60 mole ratio.
 7. A process for the manufacture of a textile article from bicomponent staple fibers comprising forming the yarn or fabric from bicomponent staple fibers in which the components exist in a sheath/core relationship and the core component has a lower melting point than the sheath component, subjecting it to a heat treatment at a temperature above the melting point of the said core component and below the melting point of the said sheath component of the bicomponent staple fibers to cause the core component to soften and exude from the end portions thereof and contact adjacent fibers, and cooling the yarn or fabric to a temperature below the melting point of the core component.
 8. A process according to claim 7 wherein the yarn to be subjected to the heat-treatment is passed over a heated plate.
 9. A process according to claim 7 wherein the fabric to be subjected to a heat treatment is treated in an air oven. 